At very high frequency RF, μWave, or mmWave systems, providing a system on a single integrated circuit (IC) presents significant challenges, since such systems often require different technologies for different components of the system. In addition, the development cycle times and development costs for state of the art custom ICs is often prohibitive for small volume applications that must be sold at low cost.
One solution to this problem is to provide hybrid microcircuits in which a number of components are produced in separate technologies and assembled on some form of substrate. At frequencies above 20 GHz, achieving low loss, good RF matching, and high isolation on printed circuit boards (PCBs) is particularly challenging. The need for high isolation requires that components be placed inside cavities, often having machined lids. This significantly increases the size, weight and cost of the assembly. In addition, providing impedance matching and low loss between components and structures in the PCB presents additional challenges.